Process and device for the intensive use of oxygen in open-hearth furnaces for producing steel



July 21, 1964 M. FORESI ETAL 3,141,763

PROCESS AND DEVICE FOR THE INTENSIVE USE OF OXYGEN IN OPEN-HEART}! FURNACES FOR PRODUCING STEEL Filed Aug. 29. 1961 United States Patent Italy Filed Aug. 29, 1961, Ser. No. 134,666 9 Claims. (Cl. 75-dtl) Processes and devices are well known which use oxygen in open-hearth furnaces for the production of steel, the oxygen being introduced into the flame and into the bath to accelerate the production of the steel. More particularly, it is known to introduce oxygen through the crown of the furnace by means of a lance which is provided with a head from which issue blasts of oxygen directed toward the bath along paths contained in vertical planes passing through the longitudinal axis of the lance. Such devices permit the use of oxygen in open-hearth furnaces, but they give rise to dangerous heat concentrations and to excessive boiling of the bath without succeeding in burning completely the reaction gases in the furnace atmosphere. Such disadvantages make it necessary to reduce the outputs and productivity of the furnace in order that the steelmaking operation may be effected without undue increase in cost due to excessive consumption of refractory materials, loss of iron and ineflicient use of oxygen.

In particular, the lances in known devices cause a penetration of oxygen into the bath and a partial removal of the slag layer in a radial direction with respect to the lon- 'gitudinal axis of the lance. However, they do not create a bath zone free of slag on which the oxygen can eflicient- 1y act and they do not produce a regular motion of the bath effective to bring fresh metal continuously under the action of the oxygen blasts.

The process and device according to the present invention avoid the above-noted disadvantages by reason of the construction of the lance head and the manner of directing the streams of oxygen.

The improved process for the intensive use of oxygen in open-hearth furnaces in accordance with the present invention is characterized by the fact that the oxygen coming from the nozzles of the lance head are directed towards the surface of the bath along lines which are slanted with respect to the plane passing through the longitudinal axis of the lance in such manner that they impart regular movements of translation and rotation not only to the slag, which is also removed by centrifugal force from the zone below the lance, but to the bath as well so that heat.

concentrations and boiling epicenters are avoided.

The above process is further characterized by the fact that in addition to the peripheral blasts along directions which are slanted with respect to the lance axis, there are provided in the central zone blasts which are less sloping, or even perpendicular to the bath, so that the oxygen coming from these blasts may act intensively on the metal to improve the efficiency of the reaction and to reduce splashing and boiling in order to prevent them from reaching and corroding the refractory materials of the furnace and to prevent them from contacting and damaging the end of the lance.

The oxygen output of each lance may be suitably adjusted and varied in accordance with the manner of operation of the burner, the direction of the flame, and the steps of the process in order to obtain a high efficiency in the process and the complete combustion of the reaction gases.

To the oxygen it is possible to add steam, or hot gases, in order to increase the speed of flow from the nozzles of 3,141,763 Patented July 21, 1964 the lance head. Other substances, carried by the oxygen, may be also added to act on the bath.

The device to carry into effect the above-described improved process is a lance of known type, which passes through the furnace crown, and is provided at its lower end with a blowing or nozzle head which is characterized by the fact that the head is formed with peripheral nozzles the axes of which are slanted with respect to the plane passing through the longitudinal axis of the lance but are slanted in the same direction around the longitudinal axis in such manner that the oxygen from the nozzles will reach the bath at separated points but with a three-component impact: vertical, radial and tangential, so that there will be obtained a wide zone of operation, free of heat concentrations and with less boiling whereby the reaction gases developed by the bath will be better burned and the slag and metal complexes will have imparted to them combined movements of translation and rotation, effective to improve the efiiciency of the process.

The sections of each nozzle are shaped in a manner to transform a portion of the oxygen pressure into kinetic energy of the blast, for the purpose of intensifying the action of displacement and circulation exerted on the slag.

In addition, there is suitably provided at least one additional nozzle contained within the imaginary surface generated by the axes ofthe peripheral nozzles, said additional nozzles having, with respect to the bath surface, a lesser slope than that of the first-mentioned nozzles, and the additional nozzle can also be perpendicular to the bath, so that the oxygen from it will cooperate with the action of the oxygen from the first set of nozzles, reaching the bath with a two-component impact, vertical and radial, in a zone inside the one reached by the nozzles of the first set to operate either metallurgically on the metal free of slag or mechanically by breaking-up any remaining areas of splashing and boiling.

The main oxygen-feed pipe is surrounded by a cooling water-shell directed downwardly and towards the head. This water-shell is, in turn, surrounded by another watershell so that the water, in passing from one to the other shell, cools the lance head conduits and nozzles. By reason of these shells, the cooling action upon the head is brought to a maximum, the cooling water reaching the head and nozzles still at a very low temperature and the inner descending column of water for transferring heat to the oxygen which, in turn, cooperates in maintaining the water of the inner descending column at a suitable low temperature.

A pipe can be added to communicate with the lance for feeding steam, or hot gases, to mix with the oxygen in order to increase its speed of flow.

A pipe can also be added to communicate with the lance to convey substances carried by the oxygen and suitable for acting on the bath.

An embodiment of the device according to the invention is shown diagrammatically, and by way of example only, in the accompanying drawings, wherein,

FIG. 1 shows in longitudinal cross-section an openhearth furnace within which are provided two lances embodying the invention;

FIG. 2 is a longitudinal cross-section on an enlarged scale, of the lance and end head shown in FIG. 1;

FIG. 3 is a perspective view, on a still further enlarged scale, of the head of the device :as seen from the inside of the outer pipe.

Referring now to FIG. 1, reference numeral 1 denotes the furnace crown through which extend the two withdrawable lances 2, each of them being provided at their ends with a head 3 for blowing oxygen onto the bath 4 which comprises a lower metal layer 5 and an upper slag layer 6. The feeding of oxygen to each lance or 3,1 3 head may be adjusted independently by valves 7 and 8. The furnace is represented in the refraining or resting stage, with burner ill in operation, burner 11 not in operation, and the flame acting in direction of arrow 12.

Referring to FIG. 2, reference numeral 2 denotes the lance body comprising an inner pipe 13 for feeding ox gen to the head 3, to which the pipe is connected by Welding 14. Head 3 is also connected by Welding 15 to the lance body 2, the end of which is closed by a casing 16 through which extend conduits 17 and 18 for blowing oxygen onto the bath. The lance body 2 has its outer surface in contact with the hot combustion gases, while its inner surfaces are engaged'by cooling water arriving through pipes 19 and Ztl and flowing between oxygen feed-pipe 13 and an intermediate pipe 21, through a perforated diaphram 22, to effectively cool head 3, conduits l7 and f3, and casing 16, and then the outer body 2 to flow out of pipes 23 and 24, following the course indicated by arrows 25. The feeding of oxygen follows arrows 26.

With reference now to FIG. 3, the reference numerals are the same as those used in the preceding figure, and arrows Z7, 27 and 27" show the direction along which the oxygen blown through conduits 1'7 succeeds in entering the bath, displacing the slag towards the periphery and imparting the combined movements of translation and rotation. The oxygen blown through inner conduit 18 acts on the metal 4 in the manner diagrammatically shown by arrows 28 and 28'.

The above-described device works as follows: the oxygen is fed separately to the two lances, the flow being adjusted, by means of valves 7 and 8, according to the operation step or stage, the flame direction and the operating conditions of the burner, to effect highly efficient operation, including the complete combustion of the reaction gases. The head at the end of each lance distributes proportionally through its conduits, the oxygen into the furnace atmosphere and onto the bath.

A first portion of oxygen is distributed in the furnace atmosphere and onto a wide outer bath zone by means of oxygen blasts which act on the bath to create a circular-radial motion, which removes the slag, said motion being partially transmitted to the metal. Owing then to the penetration, the temperature gradients and the reactions in the bath, there are other complex motions in a vertical direction, which cooperate with the above-mentioned motions to produce useful metallurgical effects.

A second portion of oxygen is distributed onto a smaller bath zone, inside the above-mentioned outer bath zone, by means of oxygen blasts which act directly on the metal free of slag, working metallurgically and mechanically to integrate and augment the effects of the first portion.

The introduction of oxygen as described, and the use of a lance having the construction of the invention make it possible to significantly improve furnace productivity and also to improve the efficiency and the control of the production process. 7

Although for describing reasons the present invention has been illustrated in terms of an illustrative embodiment, many modifications and changes can be made in carrying into effect the described process and device, especially with regard to the addition of steam and/or hot gases to the oxygen to increase its speed of flow, the addition'to the oxygen of other'substances capable of remaining in gaseous suspension to act on the bath, the number, shape and position of the conduits of the device, formal changes in the device to make it suitable for other metallurgic processes, e.g. the Linz-Donawitzs process, it being understood that all these modifications and changes fall within the scope of the invention as defined in the appended claims.

We claim:

1. An improved method for refining steel comprising, applying a plurality of concentrically arranged, angularly spaced, separate streams of gaseous fluid comprising oxygen on separate, angularly spaced, concentric impact areas arranged in a circle on an impact surface of a melt of steel, and applying said streams inclined relative to said impact surface for applying tangential forces to said melt of steel having components of force jointly and additively effective to cause rotation of material of said melt underlying said impact surface to which said streams are applied and effective to apply tangential forces having a component of force effective to eifect translation of material underlying said impact surface radially outwardly from said circle in which said impact areas are arranged.

2. An improved method for refining steel comprising,

applying a plurality of spaced, separate streams of gaseous fluid comprising oxygen on separate, spaced, impact areas on an impact surface of a melt of steel, and applying said streams inclined relative to said impact surface for applying tangential forces to said melt of steel having components of force jointly and additively effective to cause rotation of material of said melt underlying said impact surface to which said streams are applied and effective to apply tangential forces each having a component of force effective to effect translation of material underlying said impact surface radially outwardly from said circle in which said impact areas are arranged. 3. An oxygen lance for applying oxygen to a melt of steel comprising, a head, means to supply gaseous oxygen under pressure to said head, said head comprising means defining nozzles to apply a plurality of spaced streams comprising gaseous oxygen on corresponding spaced impact areas on an impact surface of said steel melt, said head comprising means to apply said stream separately and inclined relative to said impact surface on which they are applied for applying tangential forces to the material underlying said impact surface and having components of force jointly and additively effective to cause rotation of said material underlying said impact surface and for applying tangential forces each having a component of force effective to effect translation of said material underlying said impact surface in a direction radially outwardly from the impact area defined by said plurality of areas on said impact surface.

4. An oxygen lance for applying oxygen to a melt of steel comprising a head, means to supply gaseous oxygen under pressure to said head, said head comprising means defining nozzles to apply a plurality of concentrically arranged, angularly spaced streams comprising gaseous oxygen on corresponding angularly spaced concentric impact areas on an impact surface of said steel melt, said head comprising means to apply said streams separately and inclined relative to said impact surface on which they are applied for applying tangential forces to the material underlying said impact surface and having components of force jointly and additively effective to cause rotation of said material underlying said impact surface and for applying tangential forces each having a component of force effective to effect translation of said material underlying said impact surface in a direction radially outwardly from an impact circle defined by said plurality of said concentric areas on said impact surface.

5. An oxygen lance for applying oxygen to a melt of steel comprising a head, means to supply gaseous oxygen under pressure to said head, said head comprising means defining nozzles to apply a plurality of concentrically arranged, angularly spaced streams comprising gaseous oxygen on corresponding angularly spaced concentric impact areas onan impact surface of said steel melt, said head comprising means to apply said streams separately inclined relative to said impact surface on which they are applied for applying forces comprising substantially vertical force components and tangential forces to the material underlying said impact surface, said tangential forces having components of force jointly and additively effective to cause rotation of said material underlying said impact surface and for applying tangential forces each having a component of force effective to effect translation of said material underlying said impact surface in a direction radially outwardly from the impact areas defined by said plurality of areas on said impact surface.

6. An oxygen lance according to claim 5, in which said lance comprises a water jacket for cooling said head.

7. An 'oxygen lance according to claim 5, in which lance comprises means for supplying steam under pressure in said streams to increase the velocity of the gaseous oxygen in said streams.

8. An oxygen lance according to claim 5, in which said head comprises means for applying one of said streams at an inclination relative to said impact surface less than the other streams thereby to apply said one stream on the steel of said melt underlying said impact surface to 15 5 for application to said melt in said streams.

References Cited in the file of this patent UNITED STATES PATENTS 2,829,960 Vogt Apr. 8, 1958 2,878,115 Schane et al. Mar. 17, 1959 FOREIGN PATENTS 677,686 Great Britain Aug. 20, 1952 872,368 Great Britain July 5, 1961 

1. AN IMPROVED METHOD FOR REFINING STEEL COMPRISING, APPLYING A PLURALITY OF CONCENTRICALLY ARRANGED, ANGULARLY SPACED, SEPARATE STREAMS OF GASEOUS FLUID COMPRISING OXYGEN ON SEPARATE, ANGULARLY SPACED, CONCENTRIC IMPACT AREAS ARRANGED IN A CIRCLE ON AN IMPACT SURFACE OF A MELT OF STEEL, AND APPLYING SAID STREAMS INCLINED RELATIVE TO SAID IMPACT SURFACE FOR APPLYING TANGENTIAL FORCES TO SAID MELT OF STEEL HAVING COMPONENTS OF FORCE HOINTLY AND ADDITIVELY EFFECTIVE TO CAUSE ROTATION OF MATERIAL OF SAID MELT UNDERLYING SAID IMPACT SURFACE OT WHICH SAID STREAM ARE APPLIED AND EFFECTIVE TO APPLY TANGENTIAL FORCES HAVING A COMPONENT OF FORCE EFFECTIVE TO EFFECT TRANSLATION OF MATERIAL UNDERLAYING SAID IMPACT SURFACE RADIALLY OUTWARDLY FROM SAID CIRCLE IN WHICH SAID IMPACT AREAS ARE ARRANGED. 